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EP0441500A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Radio Transceiver

Assignee: Nokia Mobile Phones UK Ltd
•
Filing: 1991-01-23
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Granted: —
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Expires: 2011-01-23
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Abstract

Abstract A transceiver for a cellular telephone, particularly a portable telephone, comprises a transmitter (1) and a receiver (2) coupled to a common antenna (3) by an antenna duplex filter (4). The duplex filter (4) comprises two passband filters (5, 6) connected respectively to the transmitter (1) and the receiver (2). The receiver (2) comprises a first amplifier (7). A notch filter (8) tuned to the transmit frequency is connected to the output of the amplifier (7). The notch filter (8) enables the filtering performance of the receive filter (6) to be relaxed, and the location of the notch filter(s) at the output of amplifier (7) means that the insertion loss is less critical. The requirement for lower filtering performance enables the duplex filter (4) to be smaller and less costly.

Inventors

  • 👤 Peter Harrison

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-08 15:41
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40; H04B1/50; H04B1/52; H04B1/44; H04B1/48

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 96 words
A transceiver comprising a radio receiver and a radio transmitter operating at a different respective frequency, and duplex filtering means for coupling the receiver and the transmitter to a common antenna, the receiver including amplifying means having input means and output means, wherein the input means of said amplifying means is coupled to the duplex filtering means, characterized in that further filtering means are coupled to the output means of said receiver amplifying means, and in that the further filtering means are adapted to attenuate signals including a frequency substantially equal to the transmitter operating frequency.
Claim 2
Dependent Claim 16 words
A transceiver as claimed in claim 1, wherein the further filtering means comprises a notch filter.
Claim 3
Dependent Claim 23 words
A transceiver as claimed in claim 2, wherein means are provided for varying the frequency at which the notch filter effects maximum attenuation.
Claim 4
Dependent Claim 41 words
A transceiver as claimed in claim 3, wherein the transmitter is operable at different frequencies, and the notch filter is adapted to vary automatically the frequency at which maximum attenuation is effected in response to variations in the transmitter operating frequency.
Claim 5
Dependent Claim 27 words
A transceiver as claimed in claim 4, wherein the notch filter includes an electronically adjustable reactive device for varying the frequency at which maximum attenuation is effected.
Claim 6
Dependent Claim 44 words
A transceiver as claimed in claim 4 or claim 5, wherein means are provided for generating a control signal indicative of the transmitter operating frequency, and the frequency at which the notch filter effects maximum attenuation is varied in response to said control signal.
Claim 7
Dependent Claim 26 words
A transceiver as claimed in any of claims 3 to 6, wherein the notch filter is rendered effective at a threshold value of the transmit frequency.
Claim 8
Dependent Claim 42 words
A transceiver as claimed in claim 7, wherein the notch filter is controlled in such manner that when the transmitter frequency is below the threshold value the frequency at which the notch filter effects maximum attenuation is lower that the transmitter frequency.

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